Snarling Up Traffic

SNARLING UP TRAFFIC If you've euer driven on a major road for any distance you'll know that there are times when a jam occurs, and you slow to a crawl for a while and then pick up speed again. After a few miles of trauelling at normal speed you don't see any crash or sign of what caused the carlier snarl-up. That's because this is (probably) what happencd: Two cars travelling at steady high speed 1 of 7omph/110kh, one behind the other when the front brakes for no reason Second car slows to 6omph/95kh cars 1/4 mile (400m) behind front cars slow to 45mph/7okh cars behind the second wave (1/2m, 80om from 1st) slows on seeing brake lights in the distance to 30mph/50kh 3 Cars in fourth wave (1.5m, 2.2k behind 1st) slow sharply at apparent build-up ahead, to 15mph/25kh 4 Original cars in first row of traffic have 5 resumed speed at 7omph/110kh Cars up to 2 miles (3.sk) behind the second wave are crawling (smph/8k) in traffic build-up until front lines regain speed 2